Residential and commercial building owners are faced with the potential great water damage as a result of leaks in their plumbing systems. These leaks result from a number of causes, such as faulty or failed equipment and frozen pipes. This problem is especially acute when the property owner does not visit the building frequently as is often the case with rental property or vacation homes. For example, in Ocean City, Md., during a week long freeze in January of 1994, 345 broken pipes were reported to the Ocean City water department. Further, as a result of the same freeze, there was more than $14 million in damage reported to Maryland's top property insurers, most of which was for damage caused by frozen water pipes. Therefore the need for detecting leaks in plumbing systems and responding by shutting off the water flow can be greatly appreciated.
There are a number of automatic shutoff systems commercially available, however many of them rely on some form of moisture detection that requires the detector to be physically located where discharged water will accumulate. As a result much water damage can occur when a leak occurs in a remote area from the detector, such as an attic.
Another problem with the commercial systems is that they have limited flow span, (a ratio of the maximum flow through the device to the minimum flow detectable), and therefore have a problem detecting very low flow rates. Over a period of time, even small leaks may cause extensive damage.
Further, commercial systems do not have flow detectors with a high flow ratio, i.e. capable of detecting very low flow rates, on the order of 3-5 fluid ounces per minute while also being capable of passing large flows, 300-500 times the lowest flow, or 7-12 gallons per minute.
Another problem encountered with commercial fluid detectors with sensitivity to low flow, is that because of the sensitivity of the detector the minimum detection limit could be too low causing unwanted flow detection signals. Therefore, an adjustable low flow detection limit is needed. For example, if a bathroom commode had a slight leak and it would be inconvenient to fix it at a particular moment, one could adjust the low detection limit to a higher level to retain the safety function of the system and yet accommodate some temporary situation.